Posted on February 03 2016
Fat raindrops can kind of smack you in a tropical downpour, but it’s not painful. Snow is downright gentle, although in a blizzard it probably hits with some cold force (I wouldn’t know, having lived most of my life in the southern half of coastal California). But hail is another story. Most hail is pebble-sized and just sort of bounces off, but the mechanics of making hail can allow it to grow to truly frightening proportions.
How does hail get going, and why does it come in different sizes? Well, I’m glad you asked. Thunderstorms feature some pretty hefty updrafts which suck warm humid air up into the clouds. Water vapor in this air cools and condenses around dust particles and when it reaches a sufficient height, it freezes. Downdrafts within the clouds push the little ice crystals back down to levels where there is still water vapor that is not frozen. Some of that water collides with the crystal and sticks to it while another updraft pushes it back up to the freezing zone. This can go on repeatedly, and each round trip adds another layer of ice to the growing hailstone. In fact, the cycle will continue until a downdraft pushes the hail out of the clouds, or the stone grows too heavy for the updrafts to lift it. It should be noted that these updrafts are no mere zephyrs. At the size of a dime, hail requires a 37 mph lift; at golfball-size, a 56 mph push; and if it reaches baseball-size, 100 mph upward blasts are at play.
Hail in California is less common than it is in areas like the Midwest which is famous for thunderstorms, but statewide there are usually a couple of dozen hailstorms a year. Hail size, as noted above, is dependent upon the nature of the wind within the clouds, and record-sized hail results when conditions are just right. Recently, (Jan 26, 2016) California tied its own record for hail size. In Tehama County near Corning, northwest of Chico, hail was observed that was three inches in diameter. The only other known California hail of that size was in San Diego County some 56 years ago! The recent sky ice was special for another reason, however. Instead of being a three inch lump, it was star-shaped! Star arms and lumpy bumps on large hailstones can result from collisions with other hailstones that cause them to stick together.
Really, though, California is a piker when it comes to hail. In 2001, hail falling across eastern Kansas and southeastern Illinois hammered I-70 and caused more than $2.2 billion in damage. Dented cars and broken windshields tell you how dangerous such situations are, and you are well-advised to head for something with a solid roof when a big hailstorm hits. If caught out, you may be in for a welt-raising beating, but no more than a few deaths have ever been recorded in the U.S. as the result of hail. That may just be due to having strong buildings and being indoors a lot – China and India have experienced death tolls from tens to hundreds of victims.
Repeated blows from golfball-sized hail is bad enough, but the record for hail size in the U.S. goes to a stone that would have taken you out in one fell swoop. On July 23, 2010 in Vivian, South Dakota a hailstone eight inches in diameter weighing nearly two pounds came crashing down. It’s estimated that it took winds of 140 to 160 mph to keep that monster suspended in the clouds. Strong forces, big ice – better wear a helmet.